Welcome. I know that others know more about John Pritchard than I do so I'll wait and hope you get a good answer to your questions. Most of my research has been on the families who moved to Iowa and Illinois between 1835 and 1840, and their descendants.
Do you have any more information or can you narrow the dates at all? Are you talking about the Red River Rebellion (the first Riel Rebellion) or the Seven Oaks Massacre? Did this John have a family, and if so, can you provide some names? John was a popular name among the Pritchard family, and there were several of them. I've seen some mention of Pritchards in BC at the BC Archives and wondered how they were connected to the Red River Settlement Pritchards. Maybe you have the key.